| 摘要 |
PURPOSE: To prevent abnormal operation by enhancing the abnormality detecting function at the A/D converting section in a digital protective relay. CONSTITUTION: A multiplexer 10 repeats the operation for selecting (n) input points entirely and sequentially to deliver a signal to an A/D converting section 11 at a constant sampling period. Input points #1,..., #(n-1) are fed with AC inputs through an analog filter 8 and a sample hold circuit 9 and an input #n is fed with a voltage from negative reference voltage sources 14, 16 through a switch 17 being switched alternately at a constant sampling period. Data converted through the converter 11 is stored temporarily in a buffer memory 12 and read into an all input point operating section 7 at a constant sampling period. The operating section 7 can monitor the positive/negative converting function and accuracy, and abnormal reading of itself during A/D conversion for all input points and delivers an alarm upon detection of abnormality. |
